1. Field of the Invention
This invention relates generally to interventional medical devices, and more particularly concerns a heating catheter having variable stiffness for enhanced performance of the catheter shaft when used with or without a guide catheter, as a part of a therapeutic system or for delivery of medical devices.
2. Description of Related Art
Conventional minimally invasive catheter based therapies typically require guide wires that are one to two meters long extending through a longitudinal lumen in the catheter, and that are torqueable and pushable at the proximal end, yet soft and flexible at the distal end. Many such guidewires are made of stainless steel or the like, and are ground to tapers which provide the desired bending properties along the guidewire. Recently, numerous minimally invasive sensing and actuation procedures have been developed which benefit from the qualities of fiber optics to deliver optical light or power to the distal tip of the fiber optic. However, conventional fiber optic technology has not been easily adaptable to such applications, particularly when the fiber optic must also act as a guidewire, either within a catheter or as a stand-alone device, since fiber optics, when used alone, are not very torqueable, pushable or resilient when compared to guide wires made from a variety of other, more rigid, materials. Also, small diameter fiber optics are quite “floppy”, while larger diameter fibers can be too stiff to maneuver through sharp bends, and the use of fiber optics as guidewires or pushers within catheters can thus be difficult and quite technique sensitive.
An abdominoscope is known that includes a tubular sheath having a series of strips separated by longitudinal slots, and an elongate, steerable, flexible medical implement is also known that has a tubular body with a controllable steering region formed from flexible steering ribbons made of flexible materials, such as Nitinol, spring steel, nylon, or other plastic material. In addition, a steerable medical probe is also known that has a torque tube with spaced apart slots to impart additional flexibility to the torque tube, with a thin-walled connecting portion serving as a rib or backbone. However, there remains a need for a way of creating variable stiffness along a heating catheter, other than a fiber optic for example, without a decrease in the torquability and pushability of the heating catheter shaft.
It would also be desirable to provide a heating catheter shaft with variable stiffness to allow such heating catheters to be more pushable at the proximal end and more trackable at the distal end, and to make the use of heating catheters in catheter-based therapies more straightforward and less technique sensitive. The present invention addresses these and numerous other needs.